X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=drivers%2Fmd%2Fdm-snap.c;h=54853773510c41216c263c5096164559df7782b8;hb=6177b472ab14e1ac88896960370dd54ba577d926;hp=c01e0dafec3c0eed77fdc644e589fbbf1a424e74;hpb=515ad66cc4c82f210d726340349c8f7c1ec6b125;p=safe%2Fjmp%2Flinux-2.6 diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index c01e0da..5485377 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -71,7 +71,10 @@ struct dm_snapshot { /* List of snapshots per Origin */ struct list_head list; - /* You can't use a snapshot if this is 0 (e.g. if full) */ + /* + * You can't use a snapshot if this is 0 (e.g. if full). + * A snapshot-merge target never clears this. + */ int valid; /* Origin writes don't trigger exceptions until this is set */ @@ -80,10 +83,10 @@ struct dm_snapshot { /* Whether or not owning mapped_device is suspended */ int suspended; - mempool_t *pending_pool; - atomic_t pending_exceptions_count; + mempool_t *pending_pool; + struct dm_exception_table pending; struct dm_exception_table complete; @@ -93,6 +96,11 @@ struct dm_snapshot { */ spinlock_t pe_lock; + /* Chunks with outstanding reads */ + spinlock_t tracked_chunk_lock; + mempool_t *tracked_chunk_pool; + struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; + /* The on disk metadata handler */ struct dm_exception_store *store; @@ -102,12 +110,44 @@ struct dm_snapshot { struct bio_list queued_bios; struct work_struct queued_bios_work; - /* Chunks with outstanding reads */ - mempool_t *tracked_chunk_pool; - spinlock_t tracked_chunk_lock; - struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE]; + /* Wait for events based on state_bits */ + unsigned long state_bits; + + /* Range of chunks currently being merged. */ + chunk_t first_merging_chunk; + int num_merging_chunks; + + /* + * The merge operation failed if this flag is set. + * Failure modes are handled as follows: + * - I/O error reading the header + * => don't load the target; abort. + * - Header does not have "valid" flag set + * => use the origin; forget about the snapshot. + * - I/O error when reading exceptions + * => don't load the target; abort. + * (We can't use the intermediate origin state.) + * - I/O error while merging + * => stop merging; set merge_failed; process I/O normally. + */ + int merge_failed; + + /* + * Incoming bios that overlap with chunks being merged must wait + * for them to be committed. + */ + struct bio_list bios_queued_during_merge; }; +/* + * state_bits: + * RUNNING_MERGE - Merge operation is in progress. + * SHUTDOWN_MERGE - Set to signal that merge needs to be stopped; + * cleared afterwards. + */ +#define RUNNING_MERGE 0 +#define SHUTDOWN_MERGE 1 + struct dm_dev *dm_snap_cow(struct dm_snapshot *s) { return s->cow; @@ -248,6 +288,10 @@ struct origin { static struct list_head *_origins; static struct rw_semaphore _origins_lock; +static DECLARE_WAIT_QUEUE_HEAD(_pending_exceptions_done); +static DEFINE_SPINLOCK(_pending_exceptions_done_spinlock); +static uint64_t _pending_exceptions_done_count; + static int init_origin_hash(void) { int i; @@ -300,8 +344,10 @@ static void __insert_origin(struct origin *o) * Returns number of snapshots registered using the supplied cow device, plus: * snap_src - a snapshot suitable for use as a source of exception handover * snap_dest - a snapshot capable of receiving exception handover. + * snap_merge - an existing snapshot-merge target linked to the same origin. + * There can be at most one snapshot-merge target. The parameter is optional. * - * Possible return values and states: + * Possible return values and states of snap_src and snap_dest. * 0: NULL, NULL - first new snapshot * 1: snap_src, NULL - normal snapshot * 2: snap_src, snap_dest - waiting for handover @@ -310,7 +356,8 @@ static void __insert_origin(struct origin *o) */ static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, struct dm_snapshot **snap_src, - struct dm_snapshot **snap_dest) + struct dm_snapshot **snap_dest, + struct dm_snapshot **snap_merge) { struct dm_snapshot *s; struct origin *o; @@ -322,6 +369,8 @@ static int __find_snapshots_sharing_cow(struct dm_snapshot *snap, goto out; list_for_each_entry(s, &o->snapshots, list) { + if (dm_target_is_snapshot_merge(s->ti) && snap_merge) + *snap_merge = s; if (!bdev_equal(s->cow->bdev, snap->cow->bdev)) continue; @@ -349,9 +398,11 @@ out: static int __validate_exception_handover(struct dm_snapshot *snap) { struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; + struct dm_snapshot *snap_merge = NULL; /* Does snapshot need exceptions handed over to it? */ - if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest) == 2) || + if ((__find_snapshots_sharing_cow(snap, &snap_src, &snap_dest, + &snap_merge) == 2) || snap_dest) { snap->ti->error = "Snapshot cow pairing for exception " "table handover failed"; @@ -365,6 +416,27 @@ static int __validate_exception_handover(struct dm_snapshot *snap) if (!snap_src) return 0; + /* + * Non-snapshot-merge handover? + */ + if (!dm_target_is_snapshot_merge(snap->ti)) + return 1; + + /* + * Do not allow more than one merging snapshot. + */ + if (snap_merge) { + snap->ti->error = "A snapshot is already merging."; + return -EINVAL; + } + + if (!snap_src->store->type->prepare_merge || + !snap_src->store->type->commit_merge) { + snap->ti->error = "Snapshot exception store does not " + "support snapshot-merge."; + return -EINVAL; + } + return 1; } @@ -700,6 +772,276 @@ static int init_hash_tables(struct dm_snapshot *s) return 0; } +static void merge_shutdown(struct dm_snapshot *s) +{ + clear_bit_unlock(RUNNING_MERGE, &s->state_bits); + smp_mb__after_clear_bit(); + wake_up_bit(&s->state_bits, RUNNING_MERGE); +} + +static struct bio *__release_queued_bios_after_merge(struct dm_snapshot *s) +{ + s->first_merging_chunk = 0; + s->num_merging_chunks = 0; + + return bio_list_get(&s->bios_queued_during_merge); +} + +/* + * Remove one chunk from the index of completed exceptions. + */ +static int __remove_single_exception_chunk(struct dm_snapshot *s, + chunk_t old_chunk) +{ + struct dm_exception *e; + + e = dm_lookup_exception(&s->complete, old_chunk); + if (!e) { + DMERR("Corruption detected: exception for block %llu is " + "on disk but not in memory", + (unsigned long long)old_chunk); + return -EINVAL; + } + + /* + * If this is the only chunk using this exception, remove exception. + */ + if (!dm_consecutive_chunk_count(e)) { + dm_remove_exception(e); + free_completed_exception(e); + return 0; + } + + /* + * The chunk may be either at the beginning or the end of a + * group of consecutive chunks - never in the middle. We are + * removing chunks in the opposite order to that in which they + * were added, so this should always be true. + * Decrement the consecutive chunk counter and adjust the + * starting point if necessary. + */ + if (old_chunk == e->old_chunk) { + e->old_chunk++; + e->new_chunk++; + } else if (old_chunk != e->old_chunk + + dm_consecutive_chunk_count(e)) { + DMERR("Attempt to merge block %llu from the " + "middle of a chunk range [%llu - %llu]", + (unsigned long long)old_chunk, + (unsigned long long)e->old_chunk, + (unsigned long long) + e->old_chunk + dm_consecutive_chunk_count(e)); + return -EINVAL; + } + + dm_consecutive_chunk_count_dec(e); + + return 0; +} + +static void flush_bios(struct bio *bio); + +static int remove_single_exception_chunk(struct dm_snapshot *s) +{ + struct bio *b = NULL; + int r; + chunk_t old_chunk = s->first_merging_chunk + s->num_merging_chunks - 1; + + down_write(&s->lock); + + /* + * Process chunks (and associated exceptions) in reverse order + * so that dm_consecutive_chunk_count_dec() accounting works. + */ + do { + r = __remove_single_exception_chunk(s, old_chunk); + if (r) + goto out; + } while (old_chunk-- > s->first_merging_chunk); + + b = __release_queued_bios_after_merge(s); + +out: + up_write(&s->lock); + if (b) + flush_bios(b); + + return r; +} + +static int origin_write_extent(struct dm_snapshot *merging_snap, + sector_t sector, unsigned chunk_size); + +static void merge_callback(int read_err, unsigned long write_err, + void *context); + +static uint64_t read_pending_exceptions_done_count(void) +{ + uint64_t pending_exceptions_done; + + spin_lock(&_pending_exceptions_done_spinlock); + pending_exceptions_done = _pending_exceptions_done_count; + spin_unlock(&_pending_exceptions_done_spinlock); + + return pending_exceptions_done; +} + +static void increment_pending_exceptions_done_count(void) +{ + spin_lock(&_pending_exceptions_done_spinlock); + _pending_exceptions_done_count++; + spin_unlock(&_pending_exceptions_done_spinlock); + + wake_up_all(&_pending_exceptions_done); +} + +static void snapshot_merge_next_chunks(struct dm_snapshot *s) +{ + int i, linear_chunks; + chunk_t old_chunk, new_chunk; + struct dm_io_region src, dest; + sector_t io_size; + uint64_t previous_count; + + BUG_ON(!test_bit(RUNNING_MERGE, &s->state_bits)); + if (unlikely(test_bit(SHUTDOWN_MERGE, &s->state_bits))) + goto shut; + + /* + * valid flag never changes during merge, so no lock required. + */ + if (!s->valid) { + DMERR("Snapshot is invalid: can't merge"); + goto shut; + } + + linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk, + &new_chunk); + if (linear_chunks <= 0) { + if (linear_chunks < 0) { + DMERR("Read error in exception store: " + "shutting down merge"); + down_write(&s->lock); + s->merge_failed = 1; + up_write(&s->lock); + } + goto shut; + } + + /* Adjust old_chunk and new_chunk to reflect start of linear region */ + old_chunk = old_chunk + 1 - linear_chunks; + new_chunk = new_chunk + 1 - linear_chunks; + + /* + * Use one (potentially large) I/O to copy all 'linear_chunks' + * from the exception store to the origin + */ + io_size = linear_chunks * s->store->chunk_size; + + dest.bdev = s->origin->bdev; + dest.sector = chunk_to_sector(s->store, old_chunk); + dest.count = min(io_size, get_dev_size(dest.bdev) - dest.sector); + + src.bdev = s->cow->bdev; + src.sector = chunk_to_sector(s->store, new_chunk); + src.count = dest.count; + + /* + * Reallocate any exceptions needed in other snapshots then + * wait for the pending exceptions to complete. + * Each time any pending exception (globally on the system) + * completes we are woken and repeat the process to find out + * if we can proceed. While this may not seem a particularly + * efficient algorithm, it is not expected to have any + * significant impact on performance. + */ + previous_count = read_pending_exceptions_done_count(); + while (origin_write_extent(s, dest.sector, io_size)) { + wait_event(_pending_exceptions_done, + (read_pending_exceptions_done_count() != + previous_count)); + /* Retry after the wait, until all exceptions are done. */ + previous_count = read_pending_exceptions_done_count(); + } + + down_write(&s->lock); + s->first_merging_chunk = old_chunk; + s->num_merging_chunks = linear_chunks; + up_write(&s->lock); + + /* Wait until writes to all 'linear_chunks' drain */ + for (i = 0; i < linear_chunks; i++) + __check_for_conflicting_io(s, old_chunk + i); + + dm_kcopyd_copy(s->kcopyd_client, &src, 1, &dest, 0, merge_callback, s); + return; + +shut: + merge_shutdown(s); +} + +static void error_bios(struct bio *bio); + +static void merge_callback(int read_err, unsigned long write_err, void *context) +{ + struct dm_snapshot *s = context; + struct bio *b = NULL; + + if (read_err || write_err) { + if (read_err) + DMERR("Read error: shutting down merge."); + else + DMERR("Write error: shutting down merge."); + goto shut; + } + + if (s->store->type->commit_merge(s->store, + s->num_merging_chunks) < 0) { + DMERR("Write error in exception store: shutting down merge"); + goto shut; + } + + if (remove_single_exception_chunk(s) < 0) + goto shut; + + snapshot_merge_next_chunks(s); + + return; + +shut: + down_write(&s->lock); + s->merge_failed = 1; + b = __release_queued_bios_after_merge(s); + up_write(&s->lock); + error_bios(b); + + merge_shutdown(s); +} + +static void start_merge(struct dm_snapshot *s) +{ + if (!test_and_set_bit(RUNNING_MERGE, &s->state_bits)) + snapshot_merge_next_chunks(s); +} + +static int wait_schedule(void *ptr) +{ + schedule(); + + return 0; +} + +/* + * Stop the merging process and wait until it finishes. + */ +static void stop_merge(struct dm_snapshot *s) +{ + set_bit(SHUTDOWN_MERGE, &s->state_bits); + wait_on_bit(&s->state_bits, RUNNING_MERGE, wait_schedule, + TASK_UNINTERRUPTIBLE); + clear_bit(SHUTDOWN_MERGE, &s->state_bits); +} + /* * Construct a snapshot mapping:

*/ @@ -709,7 +1051,8 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) int i; int r = -EINVAL; char *origin_path, *cow_path; - unsigned args_used; + unsigned args_used, num_flush_requests = 1; + fmode_t origin_mode = FMODE_READ; if (argc != 4) { ti->error = "requires exactly 4 arguments"; @@ -717,6 +1060,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) goto bad; } + if (dm_target_is_snapshot_merge(ti)) { + num_flush_requests = 2; + origin_mode = FMODE_WRITE; + } + origin_path = argv[0]; argv++; argc--; @@ -733,8 +1081,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) argv++; argc--; - r = dm_get_device(ti, cow_path, 0, 0, - FMODE_READ | FMODE_WRITE, &s->cow); + r = dm_get_device(ti, cow_path, FMODE_READ | FMODE_WRITE, &s->cow); if (r) { ti->error = "Cannot get COW device"; goto bad_cow; @@ -750,7 +1097,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) argv += args_used; argc -= args_used; - r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin); + r = dm_get_device(ti, origin_path, origin_mode, &s->origin); if (r) { ti->error = "Cannot get origin device"; goto bad_origin; @@ -764,6 +1111,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) init_rwsem(&s->lock); INIT_LIST_HEAD(&s->list); spin_lock_init(&s->pe_lock); + s->state_bits = 0; + s->merge_failed = 0; + s->first_merging_chunk = 0; + s->num_merging_chunks = 0; + bio_list_init(&s->bios_queued_during_merge); /* Allocate hash table for COW data */ if (init_hash_tables(s)) { @@ -801,7 +1153,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv) INIT_WORK(&s->queued_bios_work, flush_queued_bios); ti->private = s; - ti->num_flush_requests = 1; + ti->num_flush_requests = num_flush_requests; /* Add snapshot to the list of snapshots for this origin */ /* Exceptions aren't triggered till snapshot_resume() is called */ @@ -927,7 +1279,7 @@ static void snapshot_dtr(struct dm_target *ti) down_read(&_origins_lock); /* Check whether exception handover must be cancelled */ - (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest); + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); if (snap_src && snap_dest && (s == snap_src)) { down_write(&snap_dest->lock); snap_dest->valid = 0; @@ -936,6 +1288,9 @@ static void snapshot_dtr(struct dm_target *ti) } up_read(&_origins_lock); + if (dm_target_is_snapshot_merge(ti)) + stop_merge(s); + /* Prevent further origin writes from using this snapshot. */ /* After this returns there can be no new kcopyd jobs. */ unregister_snapshot(s); @@ -1097,6 +1452,8 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success) origin_bios = bio_list_get(&pe->origin_bios); free_pending_exception(pe); + increment_pending_exceptions_done_count(); + up_write(&s->lock); /* Submit any pending write bios */ @@ -1308,6 +1665,78 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio, return r; } +/* + * A snapshot-merge target behaves like a combination of a snapshot + * target and a snapshot-origin target. It only generates new + * exceptions in other snapshots and not in the one that is being + * merged. + * + * For each chunk, if there is an existing exception, it is used to + * redirect I/O to the cow device. Otherwise I/O is sent to the origin, + * which in turn might generate exceptions in other snapshots. + * If merging is currently taking place on the chunk in question, the + * I/O is deferred by adding it to s->bios_queued_during_merge. + */ +static int snapshot_merge_map(struct dm_target *ti, struct bio *bio, + union map_info *map_context) +{ + struct dm_exception *e; + struct dm_snapshot *s = ti->private; + int r = DM_MAPIO_REMAPPED; + chunk_t chunk; + + if (unlikely(bio_empty_barrier(bio))) { + if (!map_context->flush_request) + bio->bi_bdev = s->origin->bdev; + else + bio->bi_bdev = s->cow->bdev; + map_context->ptr = NULL; + return DM_MAPIO_REMAPPED; + } + + chunk = sector_to_chunk(s->store, bio->bi_sector); + + down_write(&s->lock); + + /* Full merging snapshots are redirected to the origin */ + if (!s->valid) + goto redirect_to_origin; + + /* If the block is already remapped - use that */ + e = dm_lookup_exception(&s->complete, chunk); + if (e) { + /* Queue writes overlapping with chunks being merged */ + if (bio_rw(bio) == WRITE && + chunk >= s->first_merging_chunk && + chunk < (s->first_merging_chunk + + s->num_merging_chunks)) { + bio->bi_bdev = s->origin->bdev; + bio_list_add(&s->bios_queued_during_merge, bio); + r = DM_MAPIO_SUBMITTED; + goto out_unlock; + } + + remap_exception(s, e, bio, chunk); + + if (bio_rw(bio) == WRITE) + map_context->ptr = track_chunk(s, chunk); + goto out_unlock; + } + +redirect_to_origin: + bio->bi_bdev = s->origin->bdev; + + if (bio_rw(bio) == WRITE) { + up_write(&s->lock); + return do_origin(s->origin, bio); + } + +out_unlock: + up_write(&s->lock); + + return r; +} + static int snapshot_end_io(struct dm_target *ti, struct bio *bio, int error, union map_info *map_context) { @@ -1320,6 +1749,13 @@ static int snapshot_end_io(struct dm_target *ti, struct bio *bio, return 0; } +static void snapshot_merge_presuspend(struct dm_target *ti) +{ + struct dm_snapshot *s = ti->private; + + stop_merge(s); +} + static void snapshot_postsuspend(struct dm_target *ti) { struct dm_snapshot *s = ti->private; @@ -1336,7 +1772,7 @@ static int snapshot_preresume(struct dm_target *ti) struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; down_read(&_origins_lock); - (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest); + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); if (snap_src && snap_dest) { down_read(&snap_src->lock); if (s == snap_src) { @@ -1361,7 +1797,7 @@ static void snapshot_resume(struct dm_target *ti) struct dm_snapshot *snap_src = NULL, *snap_dest = NULL; down_read(&_origins_lock); - (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest); + (void) __find_snapshots_sharing_cow(s, &snap_src, &snap_dest, NULL); if (snap_src && snap_dest) { down_write(&snap_src->lock); down_write_nested(&snap_dest->lock, SINGLE_DEPTH_NESTING); @@ -1380,6 +1816,34 @@ static void snapshot_resume(struct dm_target *ti) up_write(&s->lock); } +static sector_t get_origin_minimum_chunksize(struct block_device *bdev) +{ + sector_t min_chunksize; + + down_read(&_origins_lock); + min_chunksize = __minimum_chunk_size(__lookup_origin(bdev)); + up_read(&_origins_lock); + + return min_chunksize; +} + +static void snapshot_merge_resume(struct dm_target *ti) +{ + struct dm_snapshot *s = ti->private; + + /* + * Handover exceptions from existing snapshot. + */ + snapshot_resume(ti); + + /* + * snapshot-merge acts as an origin, so set ti->split_io + */ + ti->split_io = get_origin_minimum_chunksize(s->origin->bdev); + + start_merge(s); +} + static int snapshot_status(struct dm_target *ti, status_type_t type, char *result, unsigned int maxlen) { @@ -1393,6 +1857,8 @@ static int snapshot_status(struct dm_target *ti, status_type_t type, if (!snap->valid) DMEMIT("Invalid"); + else if (snap->merge_failed) + DMEMIT("Merge failed"); else { if (snap->store->type->usage) { sector_t total_sectors, sectors_allocated, @@ -1465,6 +1931,13 @@ static int __origin_write(struct list_head *snapshots, sector_t sector, /* Do all the snapshots on this origin */ list_for_each_entry (snap, snapshots, list) { + /* + * Don't make new exceptions in a merging snapshot + * because it has effectively been deleted + */ + if (dm_target_is_snapshot_merge(snap->ti)) + continue; + down_write(&snap->lock); /* Only deal with valid and active snapshots */ @@ -1573,6 +2046,41 @@ static int do_origin(struct dm_dev *origin, struct bio *bio) } /* + * Trigger exceptions in all non-merging snapshots. + * + * The chunk size of the merging snapshot may be larger than the chunk + * size of some other snapshot so we may need to reallocate multiple + * chunks in other snapshots. + * + * We scan all the overlapping exceptions in the other snapshots. + * Returns 1 if anything was reallocated and must be waited for, + * otherwise returns 0. + * + * size must be a multiple of merging_snap's chunk_size. + */ +static int origin_write_extent(struct dm_snapshot *merging_snap, + sector_t sector, unsigned size) +{ + int must_wait = 0; + sector_t n; + struct origin *o; + + /* + * The origin's __minimum_chunk_size() got stored in split_io + * by snapshot_merge_resume(). + */ + down_read(&_origins_lock); + o = __lookup_origin(merging_snap->origin->bdev); + for (n = 0; n < size; n += merging_snap->ti->split_io) + if (__origin_write(&o->snapshots, sector + n, NULL) == + DM_MAPIO_SUBMITTED) + must_wait = 1; + up_read(&_origins_lock); + + return must_wait; +} + +/* * Origin: maps a linear range of a device, with hooks for snapshotting. */ @@ -1591,8 +2099,7 @@ static int origin_ctr(struct dm_target *ti, unsigned int argc, char **argv) return -EINVAL; } - r = dm_get_device(ti, argv[0], 0, ti->len, - dm_table_get_mode(ti->table), &dev); + r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &dev); if (r) { ti->error = "Cannot get target device"; return r; @@ -1631,11 +2138,7 @@ static void origin_resume(struct dm_target *ti) { struct dm_dev *dev = ti->private; - down_read(&_origins_lock); - - ti->split_io = __minimum_chunk_size(__lookup_origin(dev->bdev)); - - up_read(&_origins_lock); + ti->split_io = get_origin_minimum_chunksize(dev->bdev); } static int origin_status(struct dm_target *ti, status_type_t type, char *result, @@ -1697,11 +2200,12 @@ static struct target_type merge_target = { .module = THIS_MODULE, .ctr = snapshot_ctr, .dtr = snapshot_dtr, - .map = snapshot_map, + .map = snapshot_merge_map, .end_io = snapshot_end_io, + .presuspend = snapshot_merge_presuspend, .postsuspend = snapshot_postsuspend, .preresume = snapshot_preresume, - .resume = snapshot_resume, + .resume = snapshot_merge_resume, .status = snapshot_status, .iterate_devices = snapshot_iterate_devices, };